1. Field of the Invention
The present invention relates to a magnetic recording medium, a method for fabricating the same, and a magnetic storage device having such a magnetic recording medium. In particular, the invention relates to a patterned medium, a magnetic recording medium, and a magnetic storage device with such a magnetic recording medium that are suited to high-density recording.
2. Background Art
In recent years, there has been increasing demand for increased capacity and improved recording density of magnetic storage devices as can be seen in the recent trend that not only personal computers but other household electric appliances have also been mounted with compact, high-capacity magnetic disk devices. In order to cope with such demand, magnetic heads, magnetic recording media, and the like have been intensively developed. So far, an improvement in the areal recording density has been attempted, but nowadays, downsizing and further drastic improvement in the recording density are demanded.
Thus, there have been proposed a discrete track medium in which adjacent recording tracks are separated with a groove or a nonmagnetic material therebetween so that magnetic interference between the tracks is suppressed (for example, see Reference 1: JP Patent Publication (Kokai) No. H07-85406 A (FIG. 1)) and a patterned medium in which adjacent recording bits are separated with a groove or a nonmagnetic material therebetween so that magnetic interference between the bits is suppressed (for example, see Reference 2: JP Patent No. 3286291 B (paragraph No. [0025])).
For magnetic recording media, the planarity of the surface is considered to be very important to ensure the levitation stability of the magnetic head. When discrete track media or patterned media with high areal recording density and small magnetic domains are used, a groove between adjacent magnetic regions is filled with a nonmagnetic material as the planarity of the surface is of particular importance.
Further, discrete media and patterned media are typically provided with a protective film made of carbon-based materials above the recording layer for protection of the recording layer and adsorption of lubricant as with the conventional recording media.
Among carbon-based materials, diamond-like carbon (hereinafter also referred to as DLC) is used for the aforementioned protective film because, being amorphous, it exhibits excellent surface planarity, durability, and corrosion resistance (for example, see Reference 3: JP Patent Publication (Kokai) No. 2006-120222 A (paragraph No. [0025]))
Meanwhile, as a problem that hinders the improvement in the reliability of discrete track media and patterned media, there is a problem of corrosion due to damage caused by the process of forming projections/recesses in a magnetic film by dry-etching or the like, or corrosion due to defects or a minute gap between a magnetic region and a nonmagnetic region of the recording layer.
As an example of the conventional techniques for improving the corrosion resistance, there has been proposed a technique for improving the corrosion resistance of a soft magnetic underlayer, the corrosion of which is of the biggest concern, of a perpendicular magnetic recording medium by selecting an appropriate combination of the materials and structure of a seed layer that is provided on the soft magnetic underlayer (for example, see Reference 4: JP Patent Publication (Kokai) No. 2007-184019 A (FIG. 1)).
Further, for discrete track media and patterned media, there has also been proposed a technique for inhibiting corrosion of a magnetic region by forming a conductive film between a recording layer and a protective film (for example, see Reference 5: JP Patent Publication (Kokai) No. 2006-228282 A (paragraph No. [0051])).